In the preparation of interpolymers of .alpha.-olefins and nonconjugated dienes, the prior art such as, U.S. Pat. No. 2,933,480 teaches that with .alpha.,.omega.-dienes such as 1,7-octadiene in which all the unsaturation is terminal, both double bonds of the diolefin tend to be used up in the copolymerization with monoolefins, thus reducing the residual unsaturation which is required for good curing properties. In U.S. Pat. No. 3,900,452 aliphatic polyenes containing at least three double bonds are utilized to prepare interpolymers because an aliphatic diene can contribute to formation of saturated rings which constitute inert sites in the main chain and cannot be utilized in sulfur vulcanization. In U.S. Pat. No. 3,933,769, interpolymers prepared with 1,7-octadiene are shown to exhibit lower inherent viscosity, higher gel, and considerably lower tensile strength than the corresponding polymers prepared with the special non-.alpha.,.omega.-monomer mixture of 4- and 5-methyl-1,4-hexadienes.
C. S. Marvel and W. E. Garrison, Jr. have reported the homopolymerization of .alpha.,.omega.-diolefins of the general formula: CH.sub.2 .dbd.CH--(CH.sub.2).sub.n --CH.dbd.CH.sub.2 where n=4 to 12, 14, 18, with a triisobutylaluminum-titanium tetrachloride catalyst [J. Amer. Chem. Soc., 81, 4737 (1959)]. The polymerization of these .alpha.,.omega.-dienes yields low molecular weight polymers made up of soluble and insoluble, crosslinked portions. The soluble polymers possessed a very low molecular weight as evidenced by their sticky nature, semi-solid appearance and low inherent viscosities of the order of 0.1 dl/g. Also, the total unsaturation of the soluble polymers was considerably less than one double bond per monomer unit, indicating that cyclization had occurred.
Thus, the prior art illustrates the difficulties in preparing readily-sulfur-curable, linear interpolymers of .alpha.-olefins and .alpha.,.omega.-dienes, which preferably contain at least one double bond per .alpha.,.omega.-diene monomer unit.
We have discovered that high molecular weight, high inherent viscosity, low gel, i.e., zero to about 5 percent gel, improved-unsaturation interpolymers of .alpha.-olefins and .alpha.,.omega.-diolefins containing at least 8 carbon atoms can be prepared by modification of the organoaluminum compoundtransition metal compound catalyst systems with hexa(hydrocarbyl)phosphoric triamides or organophosphate esters. These interpolymers are quite different from those of the prior art as attested by their improved vulcanizate properties such as tensile strength, crosslink density, and swelling resistance to solvents. These interpolymers contain residual terminal olefinic double bonds which are present in pendant groups of the polymer chain and are derived from .alpha.,.omega.-dienes. The structure of a repeating unit from an .alpha.,.omega.-diene may be represented as: ##STR1## where n=4 to about 30. These olefinic double bonds are readily available as curing sites for sulfur vulcanization, resulting in the attainment of improved vulcanizate properties.
It was further found that hexaalkylphosphoric triamides and organophosphate esters will modify the organoaluminum-transition metal catalyst to give interpolymers of improved unsaturation and 0 to about 5 percent gel, which give improved vulcanizate properties. Other catalyst modifiers such as amines and phosphites do not yield interpolymers with the desired 0 to 5 percent gel and with improved unsaturation.
The data in Table I and the Examples disclosed herein illustrate the novelty of the instant invention over U.S. Pat. No. 3,933,769. This Table shows how 1,7-octadiene/1-hexene interpolymers using the modified organoaluminum-titanium trichloride catalyst give higher inherent viscosities, indicating higher molecular weight polymers, with 0 to few percent gel, compared with the corresponding 1,7-octadiene interpolymers prepared with Et.sub.3 Al/VCl.sub.4 /TiCl.sub.4 catalyst suspension over a broad range of 1,7-octadiene charge of 5-25 mole percent based on total monomers. Some of the data on these aspects are summarized in Table I. These data are selected from the various Examples in the Experimental part of the instant invention. The range of inherent viscosity data shown in Table I for the same molar charge ratio of 1-hexene to 1,7-octadiene for the interpolymers of the present invention is related to such factors as the type and amount of catalyst modifier and type and amount of the organoaluminum compound.
Table I, Example XIII, illustrate the improved vulcanizate stress-strain properties resulting from the use of the modified organoaluminum-titanium trichloride catalyst for preparation of interpolymers of the instant invention compared to interpolymers prepared with the Et.sub.3 Al/VCl.sub.4 /TiCl.sub.4 catalyst, Example (b). These improved properties result because the interpolymers of the instant invention are gel-free and possess improved unsaturation for subsequent vulcanization.
TABLE I __________________________________________________________________________ Influence of Polymerization Catalyst on Inherent Viscosity and Gel Content of the Interpolymers Derived from 1,7-Octadiene and Stress-Strain Properties of Vulcanizates. Vulcanizate Polymer Tensile Elonga- 300% Mole % Inherent % Curing Strength, tion at Modulus, Example Catalyst.sup.(a) Diene Charged Viscosity Gel Min/.degree.F. psi Break,% psi __________________________________________________________________________ .sup.(b) B 1,7-octadiene 3 4.4 3.6 35/310 1850 515 970 .sup.(b) " " 10 3.3 21.0 15/290 1510 415 1070 XIII C " 5 5.1 0 15/310 2340 505 1180 XIII D " 5 5.0 0 15/310 2170 470 1290 I E " 5 6.6 0 ND.sup.(c) ND ND ND XIII C " 10 3.5 0 15/310 2200 510 1150 V F " 10 4.1 0 ND ND ND ND VI C " 25 3.6 3 ND ND ND ND __________________________________________________________________________ .sup.(a) Catalyst B: Et.sub.3 Al/VCl.sub.4 /TiCl.sub.4, Ti/V = 3, Al/(Ti V) = 2.5. Catalyst C: Et.sub.2 AlCl/TiCl.sub.3 /[(CH.sub.3).sub.2 N].sub.3 PO, Al/T = 1.5, P/Al = 0.7. Catalyst D: Et.sub.2 AlCl/TiCl.sub.3 /(nB.sub.u O).sub.3 PO, Al/Ti = 1.5, P/Al = 0.7. Catalyst E: Et.sub.2 AlCl/TiCl.sub.3 /[(CH.sub.3).sub.2 N].sub.3 PO, Al/T = 1.5, P/Al = 0.2. Catalyst F: EtAlCl.sub.2 /TiCl.sub.3 /[(CH.sub.3).sub.2 N].sub.3 PO, Al/T = 1.5, P/Al = 0.7. .sup.(b) Data from Table II of U.S. Pat. No. 3,933,769. .sup.(c) Not Determined.
These interpolymers are formed in high conversion and also exhibit high molecular weights. Also, the interpolymers possess sufficient unsaturation to be readily sulfur-cured and have a gel content of 0 to less than 5 percent. Due to this low gel content, they are suitable for fabricating or molding goods. These interpolymers are rubbery or leathery in nature, depending on their composition. However, rubbery polymers are preferred. They are also highly ozone-resistant.
This invention is directed to sulfur vulcanizable unsaturated interpolymers of at least one terminally unsaturated monoolefin, wherein the monoolefin contains from 4 carbon atoms to about 12 carbon atoms with nonconjugated .alpha.,.omega.-dienes containing 8 to about 36 carbon atoms, wherein the said monoolefin comprises from about 95 to about 75 mole percent of the total monomers charged. Thus, the interpolymers of the present invention are prepared from about 5 to about 25 mole percent of charged .alpha.,.omega.-dienes and from about 95 to about 25 mole percent monoolefin.
Thus, the present invention is directed to the preparation of improved sulfur vulcanizable unsaturated interpolymers of at least one terminally unsaturated linear or branched monoolefin with a nonconjugated diene which is an .alpha.,.omega.-diene, thus indicating that interpolymers with one or more .alpha.,.omega.-dienes may be prepared in accordance with the practice of this invention, and said terminally unsaturated monoolefin comprises from about 95 to about 75 mole percent of the total monomer charged.
Illustrative examples of the terminally unsaturated monoolefins are: 1-butene, 1-pentene, 1-hexene, 1-heptene, 4-methyl-1-pentene, 4-methyl-1-hexene, 5-methyl-1-hexene, 1-octene, 1-decene, 1-undecene, 1-dodecene and the like. The linear monoolefins are preferred.
Illustrative examples of suitable .alpha.,.omega.-dienes containing at least 8 carbon atoms are 1,7-octadiene, 1,8-nonadiene, 1,9-decadiene, 1,10-undecadiene, 1,11-dodecadiene, 1,12-tridecadiene, 1,13-tetradecadiene, and the like.
The improved polymerization process of the present invention may be accomplished by the use of a catalytic mixture containing (A) at least one organoaluminum compound having the formula RAlX.sub.2, R.sub.3 Al.sub.2 X.sub.3, R.sub.2 AlX, or R.sub.3 Al wherein R is a hydrocarbon radical containing 1 to 12 carbon atoms and selected from the group of alkyl and/or aryl radicals and X is a halide selected from the group consisting of chloride, bromide, iodide radicals, (B) at least one compound or salt of a transition metal of Group IVB of the Periodic Table, and (C) at least one compound having the general formula: Q=P(XY.sub.n).sub.3, wherein Q is oxygen or sulfur, P is phosphorous, Y is a hydrocarbyl radical containing from 1 to 20 carbon atoms, X is oxygen, sulfur or nitrogen and n is an integer having values of 1 or 2, with the proviso that when X is oxygen or sulfur, then n is 1 and when X is nitrogen, then n is 2, as exemplified by the generic class of hexahydrocarbyl phosphoric triamides. Examples of these Y or hydrocarbyl radicals are alkyl, alkenyl, aralkyl, aryl, alkaryl and cycloalkyl radicals containing 1 to 20 carbon atoms and preferably 1 to 10 carbon atoms.
The preferred organoaluminum compounds, i.e. Component A, are the lower alkyl derivatives and the most preferred are ethylaluminum dichloride, diethylaluminum chloride, ethylaluminum sesquihalide, triethylaluminum and triisobutylaluminum.
The preferred transition metals of Component B are titanium or zirconium. The compounds of transition metals are preferably halides, oxyhalides, alkoxides and acetylacetonates. Titanium trichloride is preferred. Any crystallographic form of titanium trichloride may be used such as .alpha., .beta., .gamma., or .delta.-titanium trichloride. Catalysts derived from titanium tetrachloride may be preformed or prepared in situ.
Preferred compounds for Component C are hexaalkylphosphoric triamides or organophosphate esters. Among the specific compounds that can be used are hexamethylphosphoric triamide, triethyl trimethylphosphoric triamide, trimethyl tripropylphosphoric triamide, hexamethylthiophosphoric triamide, hexaethylthiophosphoric triamide, tri-n-butyl phosphate, triallyl phosphate, trimethyl phosphate, triethyl phosphate, O,O,O-triethylphosphorothioate, O,O,O-tri-n-butylphosphorothioate, O,O,O-trimethylphosphorothioate, trimethylphosphorotetrathioate, triethylphosphorotetrathioate, S,S,S-trimethylphosphorotrithioate, S,S,S-triethylphosphorotrithioate, O,S,S-triethylphosphorotrithioate, and the like.
Ordinarily, the transition metal compound useful in forming the catalyst is employed in an amount such as to provide about 0.0002 to 0.01, preferably about 0.0001 to 0.008 mole of transition metal compound per mole of monomers being polymerized. The organoaluminum compound is usually employed in an amount so as to provide an organoaluminum compound/transition metal compound molar ratio of about 0.5 to 15, preferably about 0.75 to 5, most preferably about 1.0 to 4.0. The Component C is usually employed in an amount so as to provide a Component C/organoaluminum compound molar ratio of about 0.1 to 2, preferably 0.2 to 1.5.
The amount of catalyst by weight is from about 0.1 to about 10 phm (parts per hundred of monomers), the preferred range being about 0.5 to 5 phm.
The polymerization can be conducted in an inert solvent. By "inert solvent" is meant one that will not adversely affect the reaction rate or reaction product. Suitable solvents are aliphatic, aromatic or cycloaliphatic hydrocarbons. Representatives of such solvents are heptane, hexane, pentane, benzene, toluene, cyclopentane, cyclohexane and the like. Chlorinated hydrocarbons such as trichloroethylene, tetrachloroethylene and chlorobenzene may be used.
The polymerization reactions involved in this invention can be carried out over a wide range of temperatures. It is convenient to carry out the process at temperatures of -20.degree. C. to 100.degree. C., preferably 0.degree. C. to 50.degree. C. The reactions may be carried out at atmospheric pressure, subatmospheric pressure, or superatmospheric pressure.